TABLE OF CONTENTS 'Confusion now hath made his masterpiece'
Shakespeare, 'Macbeth'
Preceding chapters enable the echo strength reaching the radar from passive or active targets to be calculated in presence of precipitation and in the various sea conditions. In this chapter we examine the noise and clutter which reach the detection system, competing with and perhaps masking the wanted target echoes. The competitors comprise thermal noise generated in the receiver and elsewhere, back-scatter from precipitation, sea-waves, ice or land, and possibly short-range internal feeder mismatch reflections. Their quantification prepares us to examine the signal to noise and clutter ratios necessary for calculation of target detectability in Chapter 12. Noise and clutter, by competing with wanted echoes at the radar, set a limit to the smallest detectable echo. Some aspects of precipitation and the sea were described in Chapter 5. The special characteristics of land and ice clutter were discussed in Chapter 10, Sections 10.12 and 10.13, respectively.
As far as possible radars are designed to minimise noise and reject clutters, but their natures are too signal-like for total elimination. Modern radars go far to removal of distracting clutter paints from the display. Nevertheless, if precipitation is falling around the target, or it is in a rough sea, the resulting clutter always impairs performance, even when hidden from display by a clever data extraction system. Enquiring the prevailing sea state in the approaches to a major Mediterranean port, the author was shaken to...
